In the world of Harry Potter, Hermione Granger's favorite subject is arithmancy. The novels don't offer much detail, but they make it clear that arithmancy involves the magical properties of numbers. Hermione learns to use complex charts to perform numerical divination, or tell the future using numbers.
In the real world, arithmancy is known as numerology. According to numerologists, everything in the world is dependent upon the mystical properties of numbers. These properties come from the numbers' inherent vibration. Other new-age practitioners use the term vibration to describe beliefs in the power of items like crystals, gemstones, colors and essential oils.
As the theory goes, each number has a unique vibration, giving it certain properties. These properties can shed light onto a person's behavior or predict whether romantic partners are compatible. Numerological analysis can determine a person's lucky number or lucky day. Recurring numbers can offer clues into how the world works or the significance of people and events. According to many numerologists, nothing happens by accident -- everything happens because of numbers.